Removing acids from petroleum



Dec. 27, 1960 E. M. HoNEYcuTT REMovING ACIDS FROM PETROLEUM Filed Jan. 2, 1957 United States Patent O F REMOVING ACIDS FROM PETROLEUM Earl M. Honeycutt, West Chester, Pa., assigner to Sun glil Company, Philadelphia, Pa., a corporation of New ersey Filed Jan. 2, 1957, Ser. No. 632,178

8 Claims. (Cl. 208-463) This invention relates to the removal of naphthenic acids from petroleum and the recovery of distillate oils from petroleum containing naphthenic acids.

In the refining of crude petroleum containing naphthenic acids for various uses, such as in the preparation of metallic driers, catalysts, corrosion inhibitors, etc. The removal of the naphthenic acids is also desirable from the standpoint of obtaining lubricating oils which have good quality. The lubricating oils should be neutral and should have good color and color stability. In order to obtain these results, it is necessary to substantially completely remove naphthenic acids from the lubricating oil. It is also desirable to remove naphthenic acids in order to avoid excessive corrosion of metal rening equipment.

The problem of naphthenic acid removal is particularly difficult with regard to some naphthenic crudes, e.g. Quiriquire crude, which have abnormally high naphthenic acids contents, as indicated by A.S.T.M. neutralization numbers of 1.5 mg. of KOH per gram or greater, and in some instances approaching 8 mg. of KOH per gram. Even with crudes having lower naphthenic acid contents however the problem of obtaining satisfactory naphthenic acid recovery while avoiding certain disadvantages of prior art operation, as subsequently more fully discussed, is sometimes a diiiicult one.

The present invention provides a manner of recovery of naphthenic acids and neutral, color stable lubricating oils from petroleum which avoids the disadvantages of prior art operation, and provides superior results to those previously obtainable. The process of the present invention involves, as a first stage, the extraction of at least a portion of the naphthenic acids in the unneutralized state by means of a selective solvent to obtain a solvent extract phase and a raiiinate. As a second stage, the process involves distilling the rafiinate in the presence of an alkaline material. The two stage operation according to the invention provides superior results to those obtainable by either stage in the absence of the other, or by a two stage operation in which the order of the stages is reversed.

Thus, the operation according to the invention provides results superior to those o-btainable by solvent extraction of naphthenic acids from petroleum followed by distillation of the raffinate in the absence of an alkaline material. In the latter type of operation, it is generally impossible to obtain color stable distillates even in the case where all of the naphthenic acids were removed from the petroleum in the extraction operation. It is essential in order to obtain the benefits of the invention, that the extraction be followed by a distillation involving the use of an alkaline material, the latter functioning to avoid the obtaining of unstable distillates.

The process according to the invention also provides superior results to those obtainable by distillation in they presence of an alkaline treating agent without previous removal of naphthenic acids from the petroleum charge. In the latter type of operation, it is generally impossible ICC to obtain neutral distillates from crudes which contain large amounts of naphthenic acids. Furthermore, difiiculty is encountered in such operation with respect to decomposition of organic materials in the distillation zone with resulting formation of carbonaceous deposits, fouling and pugging of the distillation apparatus, corrosion of the distillation apparatus, etc.

The process according to the invention also provides superior results to those obtained by distillation in the presence of an alkaline material, with incomplete removal of naphthenic acids, followed by solvent extraction of residual naphthenic acids from the distillates. In the latter type of operation, excessive tendency for corrosion and fouling of the distillation apparatus results. Further disadvantage resides in the fact that it is often necessary in such operation to extract a plurality of distillates, whereas in operation according to the invention, a single extraction prior to the distillation enables the obtaining of a plurality of neutral, color stable distillates.

The problem of fouling of the distillation apparatus is particularly acute in cases where a portion of the charge stock is vaporized, and the vapors are contacted with a liquid alkaline treating agent containing alkali metal hydroxide, alkali metal naphthenates and liquid hydrocarbon oil, and where naphthenic acids in the vapors react with alkali metal hydroxide to produce additional alkali metal naphthenates. In distillations where high boiling lubricating oil distillates are obtained, it is often necessary that a temperature within the approximate range from 575 F. to 725 F. be maintained in the treating zone where the vapors are contacted with the liquidl alkaline treating agent. These temperatures may be required even When reduced pressures of the order of 25 to mm. of Hg. absolute are employed. At these temperatures, there is a tendency for decomposition of alkali metal naphthenates or other organic material in the alkaline treating agent to form carbonaceous deposits which foul the metal equipment, e.g. distillation trays, in the treating Zone.

As disclosed in United States Patent No. 2,770,580, issued November 13, 1956, to Earl M. Honeycutt and vCurtiss C. Wallin, the maintaining of a high oil content in the liquid alkaline treating agent acts to reduce the amount of decomposition occurring in the treating zone. This manner of operation is effective in many instances, but its degree of eiiectiveness is dependent on the rate of introduction of alkali metal naphthenates into the liquid alkaline treating agent. Where the latter rate is relatively high, it is necessary to provide more liquid oil for the treating Zone in order to maintain the necessary cncentration of oil in the alkaline treating agent. Accordingly, superior results are obtained when the rate of introduction of alkali metal naphthenates into the treating zone is reduced, since in such case it is possible to reduce the rate of introduction of oil into the alkaline treating agent, and thereby make more oil available for the formation of lubricating oil products. Therefore, the process of the present invention is advantageous in that, by reducing the amount of naphthenic acids in the charge to the distillation, the rate of introduction of alkali metal naphthenates into the alkaline treating agent is reduced.

The charge stock for the process according to the invention is a petroleum material containing lubricating oil constituents. Crude petroleum, reduced crude, and lubricating oil distillate fractions are examples of suitable charge stocks.

Any suitable solvent which is nonreactive with naphthenic acids and has preferential solvent capacity for naphthenic acids can be employed in the extraction stage according tothe invention. The solvent is preferably more volatile than the extracted material, in order to Patented Dec. 27, 19so.

facilitate solvent recovery. However, less volatile solvents can be employed and other means employed for solvent recovery, such as addition of water to precipitate extracted material.

Various polar selective solvents are known in the art as being suitable for the selective extraction of aromatic hydrocarbon constituents from petroleum fractions. These solvents are generally suitable for use according to the invention as selective solvents for naphthenic acids, since these solvents generally have greater aiinity for the more polar compounds, and naphthenic acids are more polar than the hydrocarbon constituents of petroleum materials.

Examples of suitable selective solvents are fatty acids having 1 to 4 carbon atoms, e.g. formic acid, acetic acid, butyric acid, phenol and homologs thereof such as cresols, xylenols, etc., nitrobenzene, ,dichloroethyl ether, alcohols and ketones having 1 to 4 carbon atoms, e.g. methanol, ethanol, isopropanol, n-butanol, methyl ethyl ketone, etc., acetonitrile, liquid sulfur dioxide, etc. Modifying solvents such as water can be employed if desired. The use of furfural, though permissible, is not preferred according to the invention, since furfural tends to polymerize in the presence of acidic materials such as naphthenic acids. Various examples of suitable selective solvents are given in V. A. Kalichevsky et al., Petroleum Relining With Chemicals, pages 319 to 381 (1956), and in United States Patents Nos. 2,391,729; 2,610,209 and 2,637,744.

The conditions which are employed in the extraction stage according to the invention can be any suitable known conditions for selective solvent extraction. Preferably, the temperature is within the approximate range from 50 F. to 200 F. It is generally desirable to perform the extraction at approximately atmospheric pressure, although higher pressures can be employed if desired. The pressure should be high enough to maintain the solvent in liquid phase at the temperature employed. Preferably the amount of solvent employed is within the approximate range from 0.5 to 3 volumes of solvent per volume of charge stock on the diluent-free basis. lf desired, a suitable diluent can be employed to reduce the viscosity of the charge stock, the diluent preferably being an aliphatic hydrocarbon having an average of 5 to- 10 carbon atoms, e.g. petroleum naphtha, aviation alkylate, etc. Where diluent is employed, the amount is preferably within the approximate range fnorn 0.5 to l volume per volume of charge.

The extract obtained in the extraction stage contains naphthenic acids which have been selectively removed from the charge stock, and also generally contains naphthenic and aromatic hydrocarbons concurrently removed from the charge. The naphthenic acids can be recovered separately from the hydrocarbons by known procedures, e.g. neutralizing the naphthenic acids to form salts and extracting the latter with aqueous solutions of lower alcohols such as isopropanol.

The rafiinate obtained in the extraction preferably constitutes 60 to 99 weight percent, more preferably 80 to 95 weight percent, of the charge stock, and according to the invention is distilled to obtain naphthenic-acid-free vapors separately from a liquid alkaline material. The rai'nate usually contains a small amount of dissolved solvent, and the latter is preferably stripped therefrom prior to the distillation with alkaline material. However, such operation is not essential, and the solvent can be recovered as a separate distillate in the latter distillation. In instances where the solvent is acidic in reaction, it is converted to a salt in a distillation with alkali. During the recovery of naphthenic acids from the products of the latter distillation, the solvent is recovered as an acid which can be separated from the naphthenic acid product, for example by distillation.

Preferably the liquid alkaline material used in the distillation contains alkali metal naphthenates, e.g. sodium or potassium naphthenates, corresponding to to 90 weight percent of the naphthenic acids in the charge stock. Such naphthenates function to improve the color stability of the lubricating oils obtained as products of the distillation, and also function as dispersing agents for alkali metal hydoxide if the latter is employed in the distillation. Preferably, free alkali metal hydroxide, e.g. sodium hydroxide or potassium hydroxide, is present in the distillation zone, although in some instances it is not needed, alkali metal naphthenates being in some cases sutcient to provide the necessary color stability of the distillates. ln some instances, alkali metal hydroxide can be satisfactorily employed in the distillation in the absence of alkali metal naphthenates. However, it is preferred that naphthenates be present also.

Alkali metal naphthenates can be introduced into the distillation zone in a variety of manners. For example, in one embodiment, the raffinate obtained in the extraction contains residual naphthenic acids, as indicated by an A.S.T.M. neutralization number which is for example 0.1 to 0.9 times, more preferably 0.25 to 0.75 times, the neutralization number of the charge stock to the extraction, and such naphenic acids react with alkali metal hydroxide in the distillation zone to produce alkali metal naphthenates. In cases where the raffinate does not contain substantial amounts of naphthenic acids, the removal of naphthenic acids having been substantially complete in the extraction, alkali metal naphthenates can be introduced into the distillation zone from some other source. rl`hus for example, a portion of the naphthenic acids removed in the extraction can be introduced as alkali metal salts into the distillation zone.

Preferably, the distillation is carried out by heating the ratiinate from the extraction to a temperature within the approximate range from 650 F. to 750 F. and introducing the heated raiiinate into a flash zone maintained at a pressure within the approximate range from 25 to 100 mm. of Hg absolute, the evolved vapors being passed upwardly through a treating section containing distillation trays on which a liquid alkaline treating agent is maintained, the composition of the treating agent on the lowest tray of the treating section being preferably within the following ranges: oil 60 to 95 weight percent. alkali metal naphthenates 3 to 30 weight percent and alkali metal hydroxide 0.2 to l0 weight percent; the vapors from which naphthenic acids have been removed pass upwardly from the treating zone into a rectification zone wherein they are fractionally condensed to obtain lubricating oil products. The liquid a kaline treating agent is preferably passed continuously through the treating zone, being removed from the lowest treating tray and a portion recycled to the top treating tray. The remaining portion of the removed treating agent is preferably subjected to extraction with aqueous alcohol to remove alkali metal naphthenates therefrom. The oil from which naphthenates have been extracted is preferably recycled to the treating zone to maintain the desired oil content.

The invention will be further described with reference to the attached drawing, where Figure is a schematic iiowsheet of one embodiment according to the invention, wherein extraction of naphthenic acids from a lubricating oil distillate is performed prior to distillation in the presence of alkali, and wherein Figure 2 is a schematic 'lowsheet of another embodiment wherein crude petroleum is extracted prior to topping and the topped crude is introduced into a distillation in the presence of alkali.

Referring to Figure 1, naphthenic base crude having A.S.T.M. neutralization number of about 2.3 mg. of KOH per gram is introduced through line il into topping zone 10, which operates at atmospheric pressure for example. Gasoline, naphtha and gas oil fractions are distilled in zone l0, and removed as indicated by line 12. The reduced crude is removed through line i3 and introduced into flash zone 14. lf desired, the vapors in zone i@ can be contacted with an alkaline treating agent prior to condensation, in order to remove naphthenic acids therefrom.

In lash zone 14, a portion of the reduced crude is flashed to obtain vapors which are removed through line 16 and condensed by means not shown to produce a lubricating oil fraction. Undistilled constituents are removed as residue through line 15.

The lubricating oil condensate is introduced into extraction zone 17, wherein it is contacted with a selective solvent comprising phenol containing about 4% of water, introduced through line 13. An extract comprising a solution of, for example, 1 to 50 weight percent naph thenic acids and 50 to 99 weight percent aromatic hydrocarbons and naphthenic hydrocarbons in the phenolic solvent is removed through line 35. The rainate, having A.S.T.M. neutralization number of l mg. of KOI-I per grarn, and Saybolt Universal viscosity at 210 F. of about 50 seconds, and constituting about 85 volume percent of the charge to the extraction, is removed through line 19. After stripping of phenol therefrom if desired, by means not shown, the ranate is heated to about 675 F. by means not shown, and introduced into the flash zone of tower 20, maintained at a pressure of about 75 mm. of Hg absolute. Vapors containing lubricating oil constituents are evolved in the ash zone and passed upwardly into the alkaline treating zone. Undistilled constituents are removed as residue through line 21.

Alkali metal hydroxide, e.g. 50 B. sodium hydroxide, is introduced through line 22 to maintain the desired concentration of alkali metal hydroxide in the liquid alkaline treating agent. The treated vapors from which naphthenic acids have been substantially completely re. moved, pass upwardly into the rectification zone of tower 20. The lightest constituents of the vapors are recovered as distillate removed through line 23, and lubricating oil distillates having varying boiling range are removed as indicated by lines 24.

In the treating section, liquid alkaline treating agent introduced through line 22 passes downwardly from tray to tray countercurrent to the rising vapors. The treating agent is withdrawn through line 25, a portion thereof is recycled through line 26 to the top tray of the treating section, and another portion is introduced through line 27 into extraction zone 28, wherein it is contacted with aqueous isopropanol introduced through line 43 and petroleum naphtha introduced through line 33. The alcohol solvent extracts sodium naphthenates from the oil, and the resulting extract is removed through line 3i). Naphthenic acids can be recovered from the extract by known procedures involving treatment with sulfuric acid to liberate free naphthenic acids and separation of the liberated naphthenic acids from aqueous alcohol, the latter being recycled to the extraction zone 28 through means not shown including line 43. A naphtha solution of hydrocarbon oil is withdrawn from extraction zone 28 through line 31. Naphtha is stripped from the solution in stripping zone 32, and recycled through line 33 to zone 28. The residual oil is removed through line 34 and introduced into the treating zone of tower 20.

A portion of the alkaline treating agent withdrawn through line 25 can be introduced through means not shown into zone to provide alkaline treating agent for that zone. The treating agent removed from zone 10 can if desired be introduced into zone 28 for removal of naphthenates therefrom.

The extract removed from zone 17 is passed through line 35 into stripping zone 36, wherein phenol and water are distilled from the extract and recycled through line 37 to zone 17.` The solvent-free extract can be removed through line 38 and subsequently treated by known procedures for removal of naphthenic acids from hydrocarbons, e.g. aqueous alcohol extraction of the neutralized acids, or further extraction of the unneutral- `ized acids by the same solvent employed in the zone 17 extraction or by another solvent having preferential sol-- vent capacity for naphthenic acids, etc. VThe separated hydrocarbons can if desired be passed through means not shown including line 34, into the treating zone of tower 2t) to help maintain 4the desired oil content therein.

Instead of directly stripping solvent in zone 36, the line 35 extract can be first diluted with water to pref erentially precipitate hydrocarbons and obtain a more concentrated solution of naphthenic acids prior to introduction of the latter into the zone 36. In some cases, e.g. where an alcohol such as isopropanol is employed as solvent in zone 17, the naphthenic acids are neu tralized, e.g. with caustic soda, prior to separation of the aqueous and hydrocarbon layers, and the aqueous layer is aciditied to release naphthenic acids. The naphthenic acids are then separated in liquid phase from the aqueous alcohol, the amount of water present and the temperature being such as to provide good separation of phases.

Alternatively, the solvent-free extract can be passed through line 39 into zone 28, where the naphthenic acids are neutralized, and the resulting naphthenates recovered in the extract removed through line 30, the hydrocarbon constituents of the extract being removed in naphtha solution through line 31. If additional alkali is needed for neutralizaiton of the naphthenic acids introduced through line 39, the necessary additional alkali can be introduced through line 42.

The naphthenic acids introduced through line 39 usually have wider boiling range than those introduced as salts through line 27. The naphthenic acids recovered from the line 30 extract can be distilled to produce fractions having any desired boiling range.

Preferably, the solvent-free extract recovered from zone 36 is separately treated for naphthenic acid recovery, rather than being introduced into zone 28. In the latter case, if oil is recycled through line 34, the aromatic and naphthene hydrocarbons introduced through line 39 are introduced into tower 20 and become incorporated in the distillates. This results in a lowering of the viscosity index of the distillates, an undesirable effect in the case Vof motor lubricants for example.

On the other hand, where the distillates are to be used as rubber processing oils where aromatic and naphthene hydrocarbons are often beneficial, it is sometimes desirable to incorporate hydrocarbons from the zone 36 extract into the distillates 24. In one embodiment, this is done by introducing the extract through line 39 and recycling oil through line 34. In another embodiment, it s done by separately recovering hydrocarbons from the line 38 extract, fractionating the hydrocarbons by distillation, and blending the distillates with the corresponding distillates 24. The latter method has the advantage that the aromatic and naphthene hydrocarbons can be added to those distillates 24 which are benefitted by the addition while excluding those hydrocarbons from the distillates 24 which would be detrimentally affected by the addition.

Referring to Figure 2, naphthenic crude petroleum having neutralization number of about 2.5 mg. of KOH per gram is introduced through line 51 into extraction zone S0, wherein it is contacted with glacial acetic acid introduced through line 52 in a volume ratio, relative to crude, of 1:1. Acetic acid containing extracted naphthenic acids, aromatic hydrocarbons and naphthene hydrocarbons is removed through line 53, and is subsequently treated for recovery of naphthenic acids in any appropriate manner as previously described with regard to Figure 1.

The raffinate is removed through line 54 and introduced into topping zone 55, wherein gasoline, naphtha and gas oil are distilled and removed as indicated by line 56. A portion of the gasoline or naphtha is passed through line 58 into contact with the crude in order to act as diluent for the latter. The remainder of the distillates can be treated by suitable means'not shown to remove sm'all amounts ofacetic acid contained therein as a resillt off contamination off the rafnate with acetic acid. It desired, an alkaline treating agent can be employed intopping'zone 55, in which case the acetic acid reacts with alkaline material to produce salts, which can be removed during subsequent extraction of naphthenates from the treating agent. Topped raffinate is withdrawn through line 57 for introduction into a Itower such as the tower 20 of Figure l in the manner described for the raffinate introduced through line 19 in Figure 1. The subsequent processing is generally similar to that described in Figure 1.

In the operation described with reference to Figures land 2, ythe lubricating oil distillates obtained are neutral and have highly satisfactory color and color stability. These properties are attributable to the substantially complete removal of naphthenic acids from the vapors in the treating sectionsof the respective distillation towers. As a result of the previous extraction of a portion of the naphthenic acids from the original charge stock, complete removal of naphthenic acids can be obtained in the distillation without excessive fouling or plugging of the treating section.

The following examples illustrate the invention:

Example I Operation as illustrated in Figure 1 is carried out, the charge being a blend of 20 percent Quiriquire crude and 80 percent Coastal crude, the blend having neutralization number of about 2.3 mg. of KOH per gram and A.P.I. gravity of about 24. The lubricating oil distillate in line 16 has Saybolt Universal viscosity at 210 F. of about 60 seconds. The phenol solvent contains about 4 percent water, and the solvent-to-oil volume ratio is about 1:1. The temperature of theV extraction is about 150 F.

The raiiinate is heated to about 675 F. and introduced into the flash zone of tower 20 at a pressure of about 75 mm. of Hg absolute. The treating agent withdrawn through line 25 contains about 85 weight percent hydrocarbon oil, 13 percent sodium naphthenates and 2 percent sodium hydroxide. The lubricating oil distillates 24 have Saybolt Universal viscosities of about 85 seconds at 210 F., 500 seconds at 100 F., 200 seconds at 100 F., and 130 seconds at 100 F. respectively. A 35 volume percent aqueous solution of isopropanol is introduced through line 43, the volume ratio of aqueous isopropanol to naphthenates in the treating agent in line 27 being about 20:1. The volume ratio of naphtha to oil in the treating agent is about 1:1. The zone 28 layer separation is performed at about 110 F.

Extractl from zone 36 is treated with' a 40%' aqueous solution of isopropanol containing sodium hydroxide in amount suilicient to neutralize the naphthenic acids in the extract. An alcohol layer containing naphthenic acid salts is separated in liquid phase from a hydrocarbon layer. The alcohol layer is acidifed with sulfuric acid, and the liberated naphthenic acids are separatedY from the aqueous alcohol, the latter being recycled tol the extraction. The hydrocarbon layer is fractionally distilled to recover fractions corresponding in boiling rangeto the distiliates 24. .AV fraction obtained in the distillation of the hydrocarbon layer is blended with the corresponding distillate 24 to obtain a rubber processing oil having Saybolt Universal viscosity at 210 F. of about 85 seconds and aromatic hydrocarbon content of about 45 weight percent.

In the distillation of the hydrocarbon layer, a small amount of a base such as caustic soda is present in one embodiment in order to react with unstable constituents of the hydrocarbon layer and eliminate such constituents from thedistillates obtained. In this way, the blend of such distillate with a l-ine 24 oil results in a rubber processing oil having good color, color stability and nonstaining' properties.

The blend thus obtained, andthe other line 24 oils are S neutral and haveN.P.A. color ranging from about 3 to 5. Upon aging at 220 F. for about 16 hours, the N PLA. color increases only about one-half unit on the average for the various oils, thereby indicating good color stability.

In the operation previously described, no excessive plugging of the alkali treating zone of tower 20 occurs, nor is there excessive corrosion in any part of tower Z0 or the heating system associated therewith. By way of contrast, where highly acidic reduced crude is introduced', without previous extraction of naphthenic acids therefrom, into tower 20, it is dii'licult or impossible to prevent excessive plugging of the alkali treating zone and excessive corrosion. The plugging is attributable to excessive amounts of alkali metal naphthenates in the treating agent and consequent excessive decomposition of organic materials in the treating zone to produce carbonaceous deposits. The corrosion is attributable to the excessive amounts of acidic materials in the charge and the inability of the alkaline treating agent to remove all of the acids. This inability results further in acidic and unstable line 24 lubricating oils.

This example shows that stable, neutral oils can be obtained from highly acidic crude by extraction of a portion of the naphthenic acids from a lubricating oil distillate from such crude, followed by distillation of the rainate in the presence of alkaline material, while avoiding excessive corrosion or fouling in the distillation zone.

Example II Operation as illustrated in Figure 2 is carried out, the charge being a blend of 20 percent Quiriquire crude and percent Coastal crude, the blend having A.P.I. gravity of about 24 and A.S.T.M. neutralization number of about 2.3 mg. of KOH per gram. Glacial acetic acid in liquid form is introduced through line S2 into zone 50 at ambient temperature. One volume of gasoline is employed as diluent per three volumes of crude. The line 54 railinate constitutes more than 95 Volume percent of the crude and has A.S.T,M. neutralization number of about 1.0 mg. of KOH per gram. The line 57 reduced crude is introduced at about 675 F. into the flash zone of tower 5S at about 75 mm. of Hg absolute. The treating agent composition is approximately the same as in Example I. The properties of the lubricating oils obtained are also about the same as in Example I.

This example shows that stable, neutral oils can be obtained from highly acidic crudes by direct extraction from the crude of a portion of the naphthenic acids therein, followed by distillation of the raffinate in the presence of alkali, while avoiding excessive corrosion or fouling in the distillation zone.

In place of the blend of crudes employed in the preceding examples, Quiriquire crude having A.S.T.M. neutralization number of about 7 for example can be employed as charge stock for the extraction. Using one volume of glacial acetic acid per volume of mixture of two parts crude and one part diluent, the neutralization number is reduced for example to about 2.5. Further extraction with glacial acetic acid can be employed to further reduce the neutralization number, e.g. to about 1.

Generally similar results to those obtained in Examples I and II are obtained using other solvents in the extraction stage, e.g. nitrobenzene, aniline, ,dichloroethy1 ether, acetonitrile, liquid sulfur dioxide, etc.

The invention claimed is:

l. Process for obtaining color stable distillates of lubricating oil boiling range from highly acidic crude petroleum which comprises contacting a lubricating oil fraction charge stock containing naphthenic acids and having neutralization number of at least 1.5 mg. of KOH per gram in liquid phase with a liquid selective solvent having preferential solvent capacity for naphthenic acids, thereby to selectively extract a portion of the naphthenic acids and produce an extract containing that portion and a railinate having neutralization number 0.1 to 0.9 times the original neutralization number, vaporizing said rafnate and passing the vapors upwardly into a zone wherein they are contacted at a temperature in the range from 575 F. to 725 F. with a liquid alkaline material containing 60 to 95 weight percent of oil, 3 to 30 weight percent of alkali metal naphthenates and 0.2 to 10 weight percent of alkali metal hydroxide, thereby to condense a portion of the vapors and react naphthenic acids in the vapors with alkali metal hydroxide to form alkali metal naphthenates recoverable from the liquid alkaline material by extraction with an aqueous lower alcohol solvent, passing the vapors upwardly from said zone into a fractionating zone, and recovering from the fractionating zone distillate material having improved stability as cornpared with distillates obtained directly from said charge stock by vaporization and contact with liquid alkaline material.

2. Process according to claim 1 wherein a portion of said liquid alkaline material is removed and admixed with said extract, and wherein the resulting mixture is contacted with a lower alcohol solvent to obtain an alcohol phase containing alkali metal naphthenates and to obtain a hydrocarbon phase, and wherein the phases are separated and the hydrocarbon phase recycled to the refining zone.

3. Process according to claim 1 wherein the selective solvent is acetic acid.

4. Process according to claim 1 wherein the selective solvent is acetonitrile.

5. Process according to claim 1 wherein the selective solvent is phenol.

6. Process according to claim 1 wherein the selective solvent is nitrobenzene.

7. Process according to claim l wherein the selective solvent is liquid sulfur dioxide.

8. Process according to claim 1 wherein said charge stock is a reduced crude.

References Cited in the le of this patent UNITED STATES PATENTS 1,776,753 Edeleanu Sept. 23, 1930 1,804,451 Andrews et al May 12, 1931 2,081,498 Merrill May 25, 1937 2,701,783 Long et al Feb. 8, 1955 2,768,930 Brown et al Oct. 30, 1956 2,773,806 Kline et al Dec. l1, 1956 

1. PROCESS FOR OBTAINING COLOR STABLE DISTILLATES OF LUBRCATING OIL BOILING RANGE FROM HIGHLY ACIDIC CRUDE PETROLEUM WHICH COMPRISES CONTACTING A LUBRICATING OIL FRACTION CHARGE STOCK CONTAINING NAPHTHENIC ACIDS AND HAVING NEUTRALIZATION NUMBER OF AT LEAST 1.5 MG. OF KOH PER GRAM IN LIQUID PHASE WITH A LIQUID SELECTIVE SOLVENT HAVING PREFERENTIAL SOLVENT CAPACITY FOR NAPHTHENIC ACIDS, THEREBY TO SELECTIVELY EXTRACT A PORTION OF THE NAPHTHENIC ACIDS AND PRODUCE AN EXTRACT CONTAINING THAT PORTION AND A RAFINNATE HAVING NEUTRALIZATION NUMBER 0.1 TO 0.9 TIMES THE ORIGINAL NEUTRALIZATION NUMBER, VAPORIZING SAID RAFFINATE AND PASSING THE VAPORS UPWARDLY INTO A ZONE WHEREIN THEY ARE CONTACTED AT A TEMPERATURE IN THE RANGE FROM 575*F. TO 725*F. WITH A LIQUID ALKALINE MATERIAL CONCONTAINING 60 TO 95 WEIGHT PERCENT OF OIL, 3 TO 30 WEIGHT PERCENT OF ALKALI METAL NAPHTENATES AND 0.2 TO 10 WEIGHT PERCENT OF ALKALI METAL HYDROXIDE, THEREBY TO CONDENSE A PORTION OF THE VAPORS AND REACT NAPTHENIC ACIDS IN THE VAPORS WITH ALKALI METAL HYDROXIDE TO FORM ALKALI METAL NAPHTHENATES RECOVERABLE FROM THE LIQUID ALKALINE MATERIAL BY EXTRACTION WITH AN AQUEOUS LOWER ALCOHOL SOLVENT, PASSING THE VAPORS UPWARDLY FROM SAID ZONE INTO A FRACTIONATING ZONE, AND RECOVERING FROM THE FRACTIONATING ZONE DISTILLATE MATERIAL HAVING IMPROVED STABILITY AS COMPARED WITH DISTILLATES OBTAINED DIRECTLY FROM SAID CHARGE STOCK BY VAPORIZATION AND CONTACT WITH LIQUID ALKALINE MATERIAL. 